`pytest_sessionstart` not run in custom test directories

[padix-key]

When using a custom test directory, other than tests/ the pytest_sessionstart hook (or the maybe also the entire conftest.py) is not run. The issue appeared at pytest version 7.3.1 under Windows 10.

I created a minimum working example that shows the problem at https://github.com/padix-key/pytest-issue. When the tests folder some_path is renamed to tests pytest_sessionstart()` is sucessfully run, indicated by the raised Exception. Otherwise it is not run.

[nicoddemus]

Thanks for the reproducer, it was really helpful! Opened #10988 with a fix.